The invention pertains generally to infrared (IR) welding. More specifically, the invention relates to the use of IR heaters in the plastic welding industry to melt portions of thermoplastic components being welded together, or staked down. One example of a practical application of IR welding is the welding of two halves of an automotive plastic intake manifold together. Conventional methods of welding such manifolds utilize either hot-gas heating or infrared (IR) heating
The hot-gas method utilizes resistive heaters to heat an inert gas and blow it against the surfaces to be melted. The gas itself is the vehicle to transfer the energy to produce the melt from the resistive heater to the plastic surface. The by-product of this method is that an inert gas field surrounds the weld zone preventing oxidation or burning of the plastic. This method has little tolerance for variation in the plastic part. As the part warps closer to, or further from the heater, the temperature of the melt front varies significantly.
The IR method simply utilizes an IR heat source to radiantly heat the plastic to produce the melt. The primary advantage of the IR source is the transmission distance of the infrared energy, which is significantly greater than other means of heating the plastic. The increase in transmission distance allows the part surface to be heated much more consistently, despite variations in the distance between the heater and the part resulting from the part warping toward or away from the heater. The disadvantage of the IR heating method is that the surface of the melt being produced can oxidize or burn, causing a decrease in the strength of the weld as the two parts being welded are joined together.